Lambda values on a 2 stroke..

I was thinking about putting a lambda sensor in my header and buy a simple display to show the value to see how good/bad my jetting is. Bike is 2 stroke 300 ktm btw. But iam not sure what numbers to aim for?

12.8

However... the oils in a 2S will kill the sensor in probably 30 minutes. Hence very few people use one in a 2S (and then, only in dyno runs). If compelled, be sure to use a five wire wide band.

Thanks alot!

You can run an O2 in a 2 stroke a lot longer if you have it out of the direct exhaust stream. A few places making widebands sell adaptors that basically just space the sensor back an inch or so. Response time suffers, but for steady-state conditions that doesn't matter. Still won't last as long as a 4 stroke application, but might change that 30 minutes to a hundred hours. Run conditions, oil mix ratio, etc etc will all effect life.

14.7:1 is stoichiometric, but you will make the most power in the 12.5-13:1 range.

Amsoil makes a 2 stroke oil that claims it can be run at 130:1 in racing applications. I would use that to keep the sensor functioning.

12.8

However... the oils in a 2S will kill the sensor in probably 30 minutes. Hence very few people use one in a 2S (and then, only in dyno runs). If compelled, be sure to use a five wire wide band.

not true, we run wide-band afrs in turbo 2 stroke sleds for thousands of km each season no problems. running 25:1 with dominator, (injection pump deleted so its premix, save about 10 lbs) heat kills them though. using an extended bung with cooling fins help keep them alive.

A afr bung just after the pipe and just befor the silencer could work really well. gauge mounting would be a pain in the arse. and u would have to power it. Tuning by egt would work as well. 1250 max with a egt probe in the neck of the pipe as close to the piston crown as possible.

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